Marine biologists were able to capture these pictures of pilot whales after being given permission to dive the Strait of Gibraltar.

The small channel of water, which is busy with huge cargo ships entering and leaving the Mediterranean, is rarely dived but Rory Moore, 28, a British marine biologist, and his fellow free-divers were granted permits.

Mr Moore, from Crickhowell, Wales, said: "Some of the whales came up to the camera and started to blow bubbles and 'bark' loudly. It was an amazing thing to witness but it was actually a clear sign to keep our distance.

He said: "We think these pilot whales will have had minimal contact with humans. It's great because they are very curious and they were very keen in coming to investigate us and were looking at their reflections in the camera lens.

"But they must be treated with the upmost respect and you have to be very aware if they become aggressive.

"As toothed predators, they are more like orcas than say blue whales. There have been stories about divers being drowned after having an arm grabbed and taken into the deep.